Exploring thin-film reactions by means of simultaneous X-ray surface roughness and resistance measurements

Rapid in situ monitoring techniques during annealing of thin films are used to follow changes in phases, texture, resistivity and surface roughness as reactions between metal films and silicon substrate proceed. The characterization apparatus combines x-ray diffraction, elastic light scattering and resistivity measurements, allowing the simultaneous analysis of these three sets of characteristics. The equipment allows one to study the sequence of phases that leads to the formation of low resistivity silicides used in current microelectronic technology. The samples analyzed consisted of Ti, Co and Ni films, around 10 nm thick, on Si substrates. In the relatively simple Co-Si system no new facts were discovered. However, with Ti and Ni some metal-rich phases hitherto undetected or poorly known were set in evidence. Some comparisons are made with results obtained earlier with thicker films and different techniques, e.g. backscattering. The role of nucleation in the growth of secondary (as opposed to initial) phases is analyzed with respect to thermodynamics, reaction kinetics, and surface roughness.